This invention relates to spraying apparatus and more particularly to a unique nozzle extension for use in combination with a spray gun to facilitate spraying of a polymeric material into an enclosed cavity to completely coat the interior surfaces thereof and thus form an integral leak-proof fuel container such as, for example, an in situ formed fuel tank.
While the invention is developed for spray-coating integral aircraft fuel tanks, i.e, tanks in situ formed within the fuselage or wing cavities of an aircraft, it may also be applied to any other type vehicle including automotive type vehicles wherein the tanks are formed within the body framework of the vehicle.
According to the prior art practice of fuel tank manufacture as it pertains to aircraft, such tanks are made as a single complete unit and thereafter installed into an enclosed cavity provided for it within the confines of the aircraft framework. Tanks of the type alluded to are made by various techniques wherein fuel resistant polymeric coatings are applied to reinforcement fabric, the fabric being firstly laid up onto a mold and/or mandrel which approximates the configuration of the cavity into which the tank is to be installed. Obviously, the volume capacity of a tank made according to this practice is determined by and dependent upon how closely one is able to make the tank fit the cavity configuration.
Recent improvements in fuel resistant materials, and more particularly with respect to air-curable polyurethane elastomers, have made it feasible to make fuel tanks which are an integral part of the vehicle. This type of tank is an attractive alternative to the prior art tanks in that the total enclosed volume space provided for the tank is utilized for fuel storage which obviously allows for greater fuel capacity in a particular aircraft while also decreasing the weight of such prior art fabric-reinforced tanks. Exemplary of polyurethanes alluded to are those disclosed in U.S. Pat. No. 4,247,678 assigned to The Goodyear Tire & Rubber Company, Akron, Ohio and also in co-pending applications Ser. Nos. 502,832, now U.S. Pat. No. 4,496,707, and 502,867, now U.S. Pat. No. 4,565,729, both of which were filed on June 9, 1983.
While these polyurethane materials and/or cements have proved effective for in situ formed fuel tanks, various areas of the tank cavity are difficult, if not impossible, to cover using conventional spraying apparatus. Difficulty is especially encountered in such areas as the nooks and corners of the tank cavity and around access ports provided through the cavity for various controls such as hydraulic and/or electrical lines. Furthermore, it is extremely difficult to spray-coat the back sides of fasteners such as screws, bolts, nuts and the like which are used in fabricating the aircraft even though personnel may be able to crawl into the larger fuselage tank cavities, with the spraying equipment.
It is therefore in accordance with one aspect of the present invention an object to provide spraying apparatus that dispenses a substantially precise volume of particulate elastomeric material which when evenly dispersed over the surfaces of the cavity and cured, provides a substantially leak-proof in situ formed fuel tank within the confines of the vehicle body cavity.